EPDM vs GRP Roofing
EPDM rubber and GRP fibreglass are two of the most common flat roof systems used in the UK. This guide compares both systems for garden rooms, extensions and outbuildings — covering installation, durability, flexibility and long-term performance.
EPDM Rubber Roofing
EPDM (Ethylene Propylene Diene Monomer) is a synthetic rubber membrane widely used for flat roof waterproofing. Applied cold in a single sheet on smaller roofs, EPDM is known for its flexibility, crack bridging ability and excellent long-term weather resistance.
- Cold-applied — no hot works
- Single-piece on small roofs — no seams
- Remains flexible in cold temperatures
- Excellent crack bridging capability
- Simple cold-applied repair system
GRP (Fibreglass) Roofing
GRP (Glass Reinforced Polyester) roofing is a fibreglass system applied using resin and matting. It creates a rigid, hard surface — but this rigidity means it is more susceptible to cracking under structural movement than flexible rubber membranes like EPDM.
- Temperature-sensitive installation
- Joints required on larger roofs
- More rigid — less tolerant of movement
- Specialist installation required
- Chemical resins — ventilation needed
GRP can be suitable for certain applications but requires specialist installation and is less tolerant of structural movement than EPDM.
EPDM vs GRP — Full Comparison
| Feature | EPDM (Forti Nova) | GRP Fibreglass |
|---|---|---|
| Installation method | Cold-applied — no torch | Requires specialist resin mixing |
| Seams on small roofs | ✅ Single piece — no seams | Jointed — seams required |
| Crack bridging | ✅ Excellent — flexible rubber | ❌ More rigid — can crack |
| UV resistance | ✅ Excellent long-term | ✅ Good |
| Installation conditions | Follow the current membrane and adhesive installation guidance | Temperature and weather conditions affect resin installation |
| Repair ease | ✅ Simple cold-applied patches | Requires specialist resin |
| Environmental impact | ✅ No solvents — water-safe | Chemical resins involved |
| Suitable for garden rooms | ✅ Widely used | ✅ Used but more brittle over time |
Which Flat Roof System Is Best for Garden Rooms?
For garden rooms, home offices and residential extensions, EPDM rubber roofing is generally the preferred choice over GRP fibreglass. Its flexibility allows it to accommodate slight structural movement without cracking — a common issue with rigid GRP systems over time.
EPDM is cold-applied, meaning no hot works are required and installation can proceed in lower temperatures. On smaller roofs it can be installed as a single piece with no seams, reducing potential failure points.
Forti Nova supplies EPDM roofing systems from Blackburn alongside ground screws, steel frames and composite cladding. Collection or delivery timing is confirmed per order.
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EPDM Roofing Across the North West
Forti Nova supplies EPDM roofing systems across the North West from our Blackburn depot. Whether you're looking for EPDM roofing in Lytham, flat roof systems in Manchester or garden room roofing in Preston, collection or delivery is confirmed per order against current availability, membrane size and destination.
Need Help Choosing a Roofing System?
Our team can recommend the right waterproofing system for your roof based on substrate, area and project requirements.
01254 433987View EPDM Roofing Products